Automatic boot mounting apparatus

ABSTRACT

In an automatic boot mounting method or an apparatus for practicing the method, a wheel cylinder is held at a predetermined position, and a boot is mounted on the tapered shaft portion of an inserter. The small-diameter shaft portion of the inserter is held with an inserter moving device with the large-diameter shaft portion of the inserter faced to the cylinder body. With the inserter set along the central axis of the cylinder body, the boot is moved to the large-diameter shaft portion of the inserter by a guide plate. The inserter is moved along the central axis of the cylinder body by the inserter moving device until the end face of the large-diameter shaft portion abuts against the end face of the protrusion end portion of the piston. A first air supplying device supplies air into the boot, to inflate the boot, to fit the large-diameter sealing portion of the boot in a seal groove formed in the cylinder body, and a second air supplying device supplies air into the hydraulic pressure chamber in the cylinder body, to move the piston thereby to fit the small-diameter sealing portion of the boot in a sealing groove formed in the piston. Thus, the large-diameter sealing portion and the small-diameter sealing portion of the boot can automatically be fitted in the sealing grooves formed in the cylinder body and the piston.

This is a divisional application of application Ser. No. 08/242,876filed May 16, 1994 and now U.S. Pat. No. 5,457,865.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for mounting a boot on acylinder such as a wheel cylinder for a vehicle brake drum and ahydraulic pressure master cylinder which pressurizes an operating liquidand supplies the operating liquid thus pressurized to the wheel cylinderin such a manner that the boot covers the opening of the cylinder hole.

More particularly, the present invention relates to a boot mountingapparatus with which the annular sealing portions of a boot areautomatically fitted in the sealing grooves of a piston and a cylinderbody from outside, and to a method of mounting a boot with theapparatus.

One example of a cylinder in which a boot is mounted on a cylinder bodyand a piston in the cylinder hole of the cylinder body to cover theopening of the cylinder hole is a wheel cylinder for a vehicle drumbrake (cf. Unexamined Japanese Utility Model Publication (OPI) No. Hei.4-105643).

In the wheel cylinder, sealing grooves are formed in the outercylindrical surface of the cylinder body and in the cylindrical surfaceof the protruded end portion of the piston, and the annular sealingportions of a boot are fitted in the sealing grooves thus formed. Inorder to automatically fit the sealing portions of the boot in thesealing grooves, various apparatuses and methods have been proposed, forinstance, by Examined Japanese Patent Publication No. Hei. 3-61859,Unexamined Japanese Patent Publication (OPI) No. Hei. 3-208528, andExamined Japanese Patent Publication No. Hei. 2-28015.

The apparatus or method disclosed by the aforementioned ExaminedJapanese Patent Publication No. Hei. 3-61859 is of the outside fittingtype that the annular sealing portion is fitted in the sealing groovefrom outside. The apparatus or method disclosed by the aforementionedUnexamined Japanese Patent Application (OPI) No. Hei. 3-208528 is of theinside fitting type that the annular sealing portion is fitted in thesealing groove from inside. That is, the two prior art apparatuses andmethods are applicable to the fixing of only one of the annular sealingportions.

On the other hand, the aforementioned Examined Japanese PatentPublication No. Hei. 2-28015 is applicable to the fixing of both of theannular sealing portions. However, the prior art is stilldisadvantageous in the following point. The prior art is the combinationof the outside fitting type and the inside fitting type that one of theannular sealing portions is fitted in the sealing groove from outside,and the other is fitted in the sealing groove from inside. Hence, itcannot be applied to a cylinder such as a wheel cylinder for a vehicledrum brake in which both of the annular sealing portions are fitted inthe sealing grooves from outside. Therefore, heretofore the annularsealing portions are manually fitted in the sealing grooves, taking timeand labor.

SUMMARY OF THE INVENTION

In view of the foregoing, an object of the present invention is toprovide an apparatus in which two annular sealing portions of a boot areautomatically fitted in sealing grooves of a cylinder body and a pistonfrom the outside with high efficiency.

To achieve the foregoing object and other objects of the presentinvention, an automatic boot mounting apparatus is of the type that thelarge-diameter sealing portion of a boot is fitted in an annular sealinggroove formed in the cylindrical surface of a cylinder body while thesmall-diameter sealing portion of the boot is fitted in an annularsealing groove formed in the cylindrical surface of the protruded endportion of a piston accommodated in the cylinder hole of the cylinderbody, so that the opening of the cylinder hole is covered with the boot.The automatic boot mounting apparatus of the present invention isprovided with: a jig for holding the cylinder body at a predeterminedposition; an inserter including a large-diameter shaft portion which isequal in diameter to the protruded end portion of the piston, asmall-diameter shaft portion which is smaller in diameter than thesmall-diameter sealing portion of the boot, and a tapered shaft portionbetween the large-diameter shaft portion and the small-diameter shaftportion, the inserter having an air passageway axially extended therein;an inserter moving device for holding the small-diameter shaft portionof the inserter, and moving the inserter back and forth along thecentral axis of the cylinder body with the large-diameter shaft portionfaced towards the cylinder body; a guide plate adapted to move the bootmounted on the tapered shaft portion to the large-diameter shaftportion; a guide plate moving device for moving the guide plate back andforth along the central axis of the cylinder body; a first air supplyingdevice for supplying air through the air passageway of the inserter intoa space between the piston and the boot, to inflate the boot outwardlyto fit the large-diameter sealing portion in the sealing groove of thecylinder body; and a second air supplying device for supplying air intothe cylinder hole, to push the piston in the cylinder hole outwardly tofit the small-diameter sealing portion in the sealing groove of thepiston.

An automatic boot mounting method for use with the present invention isprovided with the steps of: providing the inserter including thelarge-diameter shaft portion which is equal in diameter to the protrudedend portion of the piston, the small-diameter shaft portion which issmaller in diameter than the small-diameter sealing portion of the boot,the tapered shaft portion between the large-diameter shaft portion andthe small-diameter shaft portion, and the air passageway extendedaxially in the inserter; moving the small-diameter sealing portion ofthe boot from the tapered shaft portion of the inserter to thelarge-diameter shaft portion of the inserter; moving the boot and theinserter towards the cylinder body so that the large-diameter shaftportion of the inserter abuts against the protruded end portion of thepiston; supplying air through the air passageway of the inserter intothe space between the boot and the piston, to inflate the boot outwardlyso as to fit the large-diameter sealing portion in the first annulargroove of the cylinder body; and supplying air into the cylinder hole topush the piston in the cylinder hole outwardly so as to fit thesmall-diameter sealing portion of the boot in the second annular groove.

The nature, utility and principle of the invention will be more clearlyunderstood from the following detailed description and the appendedclaims when read in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a diagram showing the whole arrangement of an automatic bootmounting apparatus, which constitutes an embodiment of the presentinvention;

FIG. 2 is an enlarged diagram of essential components of the apparatusshown in FIG. 1;

FIG. 3 is a sectional view of a drum brake's wheel cylinder on whichboots are mounted with the apparatus according to the present invention;

FIG. 4 is a sectional view showing an inserter and a piston which areabutted against each other during the boot mounting operation;

FIG. 5 is a sectional view showing the large-diameter sealing portion ofthe boot which is fitted in a sealing groove formed in the cylinderbody; and

FIG. 6 is a sectional view showing the small-diameter sealing portion ofthe boot which is fitted in a sealing groove formed in the piston.

DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of the present invention applied to a wheelcylinder for a vehicle drum brake will be described with reference tothe accompanying drawings.

As shown in those drawings, the wheel cylinder 2 is a hydraulic pressuretype actuator for a drum brake. The wheel cylinder 2 includes a cylinderbody 4 having a through-hole, namely a cylinder hole 5. Pistons 6 and 6are arranged in the cylinder hole 5 in such a manner that they areprotruded outside from the cylinder body 4 through both end openings ofthe cylinder hole 5, thus defining a hydraulic pressure chamber 7therebetween. An operating liquid is supplied into the hydraulicpressure chamber 7 to push out the pistons 6 and 6 to move brake shoes 8and 8 away from each other which are engaged with slits 6e formed in thepistons 6, thereby to perform a braking operation. The cylinder body 4is mounted on the back plate 10 of the drum brake 9 with fixing bolts 11and 11, with its union boss 4a protruded outside through the back plate10.

The union boss 4a has a union hole 12 which is communicated with thehydraulic pressure chamber 7. A pressurized operating liquid is suppliedinto the hydraulic pressure chamber 7 through a union bolt (not shown)engaged with the opening of the union hole 12. Each piston 6 includes acylindrical body 6a which is adapted to slide in the cylinder hole 5 andhas a sealing groove 6d in the cylindrical surface. A cup seal 13 isfitted in the sealing groove 6d to make the hydraulic pressure chamber 7liquid-tight. A boot. 3 is set over a protruded end portion 6b having asmall diameter which is extended from the cylindrical body 6a laterallyof the cylinder body 4, in such a manner as to cover the cylindricalsurface of the end portion of the cylinder body 4, so as to prevent theentrance of water or dust into the cylinder hole 5.

One end portion of the boot 3 is formed into a large-diameter annularsealing portion 3a, and the other end portion is formed into asmall-diameter annular sealing portion 3b. With an automatic bootmounting apparatus 1, the large-diameter annular sealing portion 3a isautomatically fitted in a sealing groove 4b formed in the cylindricalsurface of the cylinder body 4, while the small-diameter annular sealingportion 3b is automatically fitted in a sealing groove 6c formed in thecylindrical surface of the protruded end portion 6b.

The automatic boot mounting apparatus 1 is provided with a jig 20 forholding the wheel cylinder 2, an inserter 30 for guiding the mounting ofthe boot 3, an inserter moving device 40 for moving the inserter 30 to apredetermined mounting position, a guide plate 50 for moving the boot 3into which the inserter 30 is inserted, a guide plate moving device 60for moving the guide plate 50, a first air supplying device 70, and asecond air supplying device 80.

One set of the above-described components 30, 40, 50, 60, 70 and 80 areprovided on one side of the jig 20, and another set of the samecomponents 30 through 80 are provided on the other side of the jig 20,so that two boots 3 and 3 can be mounted on both ends of the wheelcylinder 2, respectively, at the same time. Those components 30 through80 on both sides of the jig 20 are arranged symmetrically with respectto the jig 20. Hence, for simplification in description, only thecomponents 30 through 80 on the right-hand side of the jig 20 will bedescribed.

The jig 20 includes a plate-shaped stand 22 fixedly mounted on top of aguide support 21. The plate-shaped stand 22 has a pair of guide bosses22a and 22a, and a guide hole 22b. The wheel cylinder 2 is fixed asfollows: The guide bosses 22a and 22a are engaged with female-threadedholes 4c and 4c of the cylinder body 4 into which the fixing bolts 11are screwed. With the union boss 4a engaged with the guide hole 22b, thewheel cylinder 2 is positioned on the upper surface of the stand 22.Under this condition, a clamping device (not shown) is used to fix thewheel cylinder 2.

The inserter 30 is substantially in the form of a tapered shaft. Theinserter 30 includes: a large-diameter shaft portion 30a which is equalin diameter to the protruded end portion 6b of the piston 6, and islarger in diameter than the small-diameter annular sealing portion 3b ofthe boot 3; a small-diameter shaft portion 30b which is smaller indiameter than the small-diameter sealing portion of the boot 3; and atapered shaft portion 30c between the above-described shaft portions 30aand 30b. The inserter 30 has a through-hole, namely, a second airpassageway 73 along the axis which is a part of the first air supplyingdevice 70. The boot 3 is mounted on the inserter 30 as follows: With thelarge-diameter sealing portion 3a of the boot 3 on the side of thelarge-diameter shaft portion 30a of the inserter 30, the inserter 30 isinserted into the boot 3 beginning from the small-diameter shaft portion30b until the small-diameter sealing portion 3b is caught by the taperedshaft portion 30c at a portion where the diameter of the tapered shaftportion 30c is equal to that of the small-diameter sealing portion 3b.Thus, the boot 3 has been mounted on the inserter 30.

An inserter moving device 40 includes: a first operating cylinder 41 fora collet cap 46; a collet holder 43 which, together with the operatingcylinder 41, is fixedly secured to a bracket 42; a pair of joints 45 and45 which are, held through a coupling board 44 on the push rod 41a ofthe first operating cylinder 41; the aforementioned collet cap 46 whichis held on the front ends of the joint rods 45 and 45 to cover the frontend portion of the collet holder 43; and a collet 47 which is set notonly inside the cap 46 but also inside the collet holder 43.

The collet holder 43, the collet cap 46, and the collet 47 are arrangedcoaxially with the cylinder body 4. The joint rods 45 and 45 areparallel with the central axis of the cylinder body 4. The collet cap 46is reciprocated along the central axis of the cylinder body 4 by thepush rod 41a which is moved back and forth by the first operatingcylinder 41.

The collet holder 43 has a tapered hole 43a for accommodating the collet47, and a first air passageway 72 which is a part of the first airsupplying device 70. The collet 47 is a kind of chuck which is formed bycutting a plurality of slits in both end portions of a conical memberalternately so as to be expandable and contractible. That is, the collet47 has a tapered cylindrical outer surface 47a, through which the collet47 is inserted into the tapered hole 43a of the collet holder 43. Thecollet 47 has an inserting through-hole 47b, into which thesmall-diameter shaft portion 30b of the inserter 30 is inserted. Morespecifically, the small-diameter shaft portion 30b is inserted until itsfront end comes in the first air passageway 72.

As the collet cap 46 is moved to the right in FIG. 1 or 2 by theoperation of the first operating cylinder 41, the collet 47 into whichthe small-diameter shaft portion of the inserter 30 has been inserted ispushed into the collet holder. In this operation, the diameter of thecollet 47 is gradually decreased by the tapered hole 43a of the colletholder 43; that is, the collet 47 grips the small-diameter shaft portion30b of the inserter. As the collet cap 46 is moved to the left-handedside in FIG. 1 or 2, the collet 47 is gradually expanded while movingaway from the collet holder, which permits the removal of thesmall-diameter shaft portion 30b of the inserter 30.

The guide plate 50 is hat-shaped in section, with its central portionprotruding toward the wheel cylinder 2. The guide plate 50 has aninserting through-hole 50a whose diameter is substantially equal to thatof the large diameter shaft portion 30a of the inserter 30. Thesmall-diameter shaft portion 30b of the inserter 30 is inserted throughthe inserting through-hole 50a and the inserting through-hole 47b of thecollet 47 into the collet holder 43.

The guide plate moving device 60 includes a pair of second operatingcylinders 61 and 61 which are set above and below the inserter movingdevice 40. The middle portion of the push rods 61a of the secondoperating cylinders 61 are supported through holders 62 on theabove-described bracket 42, and the front ends of the push rods 61a arecoupled to the guide plate 50. Hence, as the push rods 61a and 61a ofthe second operating cylinders 61 and 61 are moved back and forth, theguide plate 50 is moved back and forth along the central axis.

As was described above, the small-diameter sealing portion 3b of theboot 3 is mounted on the tapered shaft portion 30c of the inserter 30.When, under this condition, the second operating cylinders 61 and 61 areoperated to move the guide plate 50 towards the cylinder body, thesmall-diameter sealing portion 3b is pushed toward the large-diametershaft portion 30a of the inserter 30 while being expanded by the taperedshaft portion 30c. Finally, the small-diameter sealing portion 3b ismounted on the large-diameter shaft portion 30a of the inserter 30.

The inserter moving device 40, the guide plate 50, and the guide platemoving device 60 are provided in a slide mechanism 90 indicated by thetwo-dot chain line in FIG. 1 or 2. The inserter moving device 40, theguide plate 50, the guide plate moving device 60, and the inserter 30held by the collet 47 of the inserter moving device 40 can be moved backand forth along the central axis of the cylinder body 4 by the push rod91a of a third operating cylinder 91 which is coupled to the slidemechanism.

The first operating cylinder 41 of the inserter moving device 40 iscoupled to the push rod 100a of a fourth operating cylinder 100 which isfixedly provided outside the slide mechanism 90, so that the insertermoving device 40 is moved back and forth along the central axis of thecylinder body 4, independently of the guide plate 50 and the guide platemoving device 60.

The first air supplying device 70 includes: a compressing machine 71such as a compressor or blower; the first air passageway 72 in thecollet holder 43; the second air passageway 73; and a supply pipe 74through which the compressing machine 71 is connected to the first airpassageway 74. The air compressed by the compressing machine 71 is blownout through the second air passageway 73 of the inserter 30.

The second air supplying device 80 includes: a compressing machine 81; afifth operating cylinder 82 with a fixing board on the ends of the pushrods 82a; an inserter block 84 held on the fixing board 83; and aninserter 85 connected to the end of the inserter block 84. The inserter85 is made of an elastic material such as urethane resin. By the liftingoperation of the fifth operating cylinder 82, the inserter 85 is engagedwith the union hole 12 of the wheel cylinder 2, so that the aircompressed by the compressing machine 81 is supplied into the cylinderhole 5.

The embodiment thus organized operates as follows.

First, the cylinder body 4 of the wheel cylinder 2 is held with the jig20 in the above-described manner. The components except the boots 3 and3 on both sides have been coupled to the cylinder body 4. The pistons 6and 6 inserted in the cylinder body 4 are urged outward by a returnspring 14 which is elastically set in the hydraulic pressure chamber 7,so that the sealing grooves 6c of the protruded end portions 6b of thepistons 6 are exposed outside the cylinder body 4 on both sides.

Before the collet 47 holds the inserter 30, the inserter moving device40, the guide plate 50, and the guide plate moving device 60 are attheir retracted positions because the slide mechanism 90 is pulled bythe third operating cylinder 91. The collet cap 46, being pushed by thefirst operating cylinder 41, is moved towards the cylinder body 4, sothat the inserting through-hole 47b of the collet 47 is expanded.

Each of the boots 3 to be coupled to the wheel cylinder 2 is mounted onthe tapered shaft portion 30c of the inserter 30 with the large-diametersealing portion 3a facing the large-diameter shaft portion 30a. Afterthe boot 3 has been mounted on the inserter 30 in the above-describedmanner, the small-diameter shaft portion 30b is inserted through theinserting through-hole 50a of the guide plate 50 and the insertingthrough-hole 47b of the collet 47 into the first air passageway 73.Under this condition, the first operating cylinder 41 is operated tomove the collet cap 46 in the direction which is opposite to thedirection in which the cylinder body is located (hereinafter referred tomerely as "backwardly", when applicable), and the small-diameter shaftportion 30b is chucked with the collet 47. As a result, the inserter 30is set along the central axis of the cylinder body 4, while the boot 3mounted on the tapered shaft portion 30c of the inserter 30 is broughtinto contact with the front end face of the guide plate 50 (as shown inFIGS. 1 and 2).

Thereafter, the third operating cylinder 91 is operated to push theslide mechanism 90, so that the inserter moving device 40, the guideplate 50, and the guide plate moving device 60 are moved, as one unit,towards the cylinder body 4 to cause the end face of the large-diametershaft portion 30a of the inserter 30 to strike against the end face ofthe protruded end portion 6b of the piston 6 until the piston 6 issomewhat pushed into the cylinder hole 5. Before or after thisoperation, the guide plate 50 is moved towards the cylinder body by thefirst operating cylinder, so that the boot 3 mounted on the taperedshaft portion 30c of the inserter 30 is moved to the large-diametershaft portion 30a, and the large-diameter sealing portion 3a isprotruded over the large-diameter shaft portion 30a and then pressedagainst the end face of the cylinder body 4 as shown in FIG. 4. As aresult, an air chamber 15 is formed between the cylindrical body 6a ofthe piston 6 and the end portion of the large-diameter shaft portion 30aof the inserter 30 with which the small-diameter sealing portion 3b ofthe boot 3 is engaged.

When compressed air is provided by the compressing machine 71 of thefirst air supplying device 70, the compressed air is supplied throughthe second air passageway 73 of the inserter 30 and the slit 6e in theprotruded end portion 6b into the air chamber 15, so that thelarge-diameter sealing portion 3a of the boot 3 is inflated outwardly bythe compressed air as indicated by the two-dot chain lines in FIG. 5.The large-diameter sealing portion 3a thus inflated is moved over theperiphery of the protruded end portion, and finally engaged with thesealing groove 4b of the cylinder body 4 as shown in FIG. 5. Thereafter,the compressing machine 71 is operated in the reverse direction, or anair discharging device (not shown) such as a valve is operated todischarge the air from the air chamber 15. As a result, thelarge-diameter sealing portion 3a is restored; i.e., contracted, thusbeing fitted in the sealing groove 4b of the cylinder body 4 asindicated by the solid lines in FIG. 5.

Thereafter, the fifth operating cylinder 82 of the second air supplyingdevice 80 is operated to raise the push rods 82a thereby to engage theinserter 85 with the union hole 12 of the cylinder body 4. Under thiscondition, the compressing machine 81 of the second air supplying device80 is operated to produced compressed air. The compressed air issupplied through the union hole 12 into the hydraulic pressure chamber 7in the cylinder hole 5, so that the right and left pistons 6 and 6 inthe cylinder hole 5 are pushed outwardly.

At the same time, the fourth operating cylinder 100 is operated toretract its push rod, so that the inserter moving device 40 is movedbackwardly, away from the cylinder body. As a result, the large-diametershaft portion 30a of the inserter 30 is pulled out backwardly (to theright in FIG. 6) leaving the boot 3 supported by the guide plate 50. Asthe inserter 30 is retracted, the piston 6 is moved outwardly.

When the large-diameter shaft portion 30a of the inserter 30 isdisengaged from the small-diameter sealing portion 3b of the boot 3, theprotruded end portion 6b of the piston 6 is engaged with thesmall-diameter sealing portion 3b. The small-diameter sealing portion 3bengaged with the protruded end portion 6b is moved on the cylindricalsurface of the protruded end portion 6b as the piston 6 is movedoutwardly. When the small-diameter sealing portion 3b comes to thesealing groove 6c of the piston 6, it is contracted and fitted in thesealing groove 6c as shown in FIG. 6.

When necessary, the compressed air is supplied into the hydraulicpressure chamber 7 by the second air supplying device 80, and the fourthoperating cylinder 100 is operated, so that the piston 6 and theinserter 30 are moved back and forth along the central axis of thecylinder body, whereby the large-diameter sealing portion 3a and thesmall-diameter sealing portion 3b are sufficiently fitted in the sealinggrooves 4b and 6c.

The present invention has been described with reference to the wheelcylinder of the vehicle drum brake; however, the present invention isnot limited thereby or thereto. That is, the technical concept of thepresent invention may be widely applied to cylinders on each of whichthe large-diameter sealing portion and the small-diameter sealingportion of the boot are to be mounted from outside.

As was described above, the two annular sealing portions of the boot areautomatically mounted on the cylinder from outside according to thepresent invention. That is, when compared with the prior art in whichthe boot is manually mounted on the cylinder or only one of the twosealing portions of the boot is mounted on the cylinder, the presentinvention is advantageous in that the time required for mounting theboot on the cylinder can be greatly reduced. That is, the apparatus ofthe invention is high in productivity, and the product formed thereby islow in manufacturing cost. Furthermore, the burden on the worker isgreatly decreased, and the sealing performance of the boot is lessfluctuated; that is, it is stable at all times.

While there has been described a preferred embodiment of the presentinvention, it will be obvious to those skilled in the art that variouschanges and modifications may be made therein without departing from theinvention, and it is aimed, therefore, to cover in the appended claimsall such changes and modifications as fall within the true spirit andscope of the invention.

What is claimed is:
 1. An automatic boot mounting apparatus for mountinga boot on a cylinder, said cylinder having a cylinder body including acylinder hole and a first annular groove formed on an end of an outersurface thereof, and a piston accommodated in said cylinder hole of saidcylinder body, said piston including a protruded end portion and asecond annular groove formed on an outer surface of said protruded endportion, and said boot including a large-diameter sealing portion forbeing fitted in said first annular groove and a small-diameter sealingportion for being fitted in said second annular groove; said automaticboot mounting apparatus comprising:an inserter including alarge-diameter shaft portion which is equal in diameter to saidprotruded end portion of said piston, a small-diameter shaft portionwhich is smaller in diameter than said small-diameter sealing portion ofsaid boot, a tapered shaft portion interconnecting said large-diametershaft portion and said small-diameter shaft portion, and an airpassageway extending axially through said shaft portions; a slidemechanism for moving each of said inserter and said boot along a centralaxis of said cylinder body and toward said cylinder body, said slidemechanism including a guide plate axially movable relative to saidinserter for moving said boot along a length of said inserter; first airsupplying means for supplying air through said air passageway into aspace between said piston and said boot, to fit said large-diametersealing portion in said first annular groove by inflating said bootoutwardly; and second air supplying means for supplying air into saidcylinder hole, to fit said small-diameter sealing portion in said secondannular groove by pushing said piston outwardly from said cylinder body.2. The automatic boot mounting apparatus of claim 1, wherein said slidemechanism comprises:inserter moving means for holding saidsmall-diameter shaft portion, and for moving said inserter along thecentral axis of said cylinder with said large-diameter shaft portionfacing said cylinder; said guide plate moving said boot mounted on saidtapered shaft portion towards said large-diameter shaft portion; andguide plate moving means for moving said guide plate along saidinserter.
 3. The automatic boot mounting apparatus of claim 2, whereinsaid guide plate moving means comprises:at least one guide plate pushrod positioned parallel to said central axis and connected to said guideplate; and a guide plate operating cylinder associated with said atleast one guide plate push rod.
 4. The automatic boot mounting apparatusof claim 2, wherein said inserter moving means further comprises:acollet for holding said small-diameter shaft portion; and a colletholder connected to said collet, including an opening for receiving saidcollet, wherein, when said small-diameter shaft portion is inserted intosaid inserter moving means, said collet is compressed by said colletholder and said inserter is held in place.
 5. The automatic bootmounting apparatus of claim 1, further comprising a jig for holding saidcylinder at a predetermined position.
 6. The automatic boot mountingapparatus of claim 5, wherein said jig comprises:a plurality of guidebosses supporting said cylinder; a stand connected to said guide bosses;and a guide support connected to said stand and to said second airsupplying means.
 7. A system for mounting a boot on a cylinder, saidcylinder having a cylinder body including a cylinder hole and a firstgroove formed on an end of an outer surface thereof, and a pistonaccommodated in said cylinder hole of said cylinder body, said pistonincluding a protruded end portion and a second groove formed on an outersurface of said protruded end portion, and said boot including afirst-diameter sealing portion for being fitted in said first groove anda second-diameter sealing portion for being fitted in said secondgroove, said system comprising at least two automatic boot mountingdevices positioned on opposite sides of said cylinder body, each saidautomatic boot mounting device comprising:an inserter including afirst-diameter shaft portion which is equal in diameter to saidprotruded end portion of said piston, a second-diameter shaft portionwhich is smaller in diameter than said second-diameter sealing portionof said boot, a third shaft portion interconnecting said first-diametershaft portion and said second-diameter shaft portion, and an airpassageway extending axially through said shaft portions; a slidemechanism for moving each of said inserter and said boot along a centralaxis of said cylinder body and toward said cylinder body, said slidemechanism including a guide plate axially movable relative to saidinserter for moving said boot along a length of said inserter; first airsupplying means for supplying air through said air passageway into aspace between said piston and said boot, to fit said first-diametersealing portion in said first groove by inflating said boot outwardly;and second air supplying means for supplying air into said cylinderhole, to fit said second-diameter sealing portion in said second grooveby pushing said piston in said cylinder hole outwardly from saidcylinder body.
 8. An apparatus for mounting a boot on a body and on apiston extending from said body, comprising:a guide plate having a firstopening; an inserter positionable within said first opening and havingan air passageway extended axially therethrough; means for positioningsaid inserter within said first opening; means for moving said guideplate along the length of said inserter; means for supplying air throughsaid air passageway; and means for supplying air to said body forextending said piston from said body, said piston having a firstdiameter, said boot including a first opening having a first diameterand a second opening having a second diameter for mounting on saidpiston, said inserter having a first shaft portion having said firstdiameter, a second shaft portion having a diameter smaller than saidsecond diameter and a tapered third shaft portion interconnecting saidfirst shaft portion and said second shaft portion, said guide plate formoving said boot axially along said inserter, said means for positioningsaid inserter for moving said inserter adjacent said piston such thatsaid guide plate and said first and second means for supplying air causesaid boot to be sequentially mounted on said body and then on saidpiston.